The OTA provides a way for an IOTACodeInsightManager100 to handle GotoDefinition.
Before Denali, the IDE would use the Syntax Highlight information for the file to determine when GotoDefinition was valid; but that has changed now: there's a new interface, IOTACodeInsightUIOverride that you can implement: its member EnableGotoDefinition allows you to tell the IDE when GoToDefinition is valid for any location in a file your CodeInsightManager handles. So now, an implementation of IOTACodeInsightManager100 can make the IDE handle CTRL-CLICK even on a comment
In 2017, with the release of Delphi 10.2 Tokyo, Embarcadero introduced a specialized implementation of the Observer pattern into the System.Classes unit. While it has been in the wild for 9 years, it remains a "hidden" architecture for many, primarily because it serves as the invisible engine behind LiveBindings. Other than live bindings, you can also use the Observer pattern as a way to update component settings to the Windows registry, an .ini file, or persist it elsewhere.
System.Classes